Directed self-assembly (DSA) of block copolymers is drawing an increasing amount of attention as a technology allowing surface patterns to be produced at the nanoscale, thereby surmounting lithography resolution limits. In particular, this technology seems to be well suited to the production of patterns of lines (conductive tracks) and holes (VIAs) in next-generation integrated circuits.
The separation of the phases of block copolymers (BCPs) forms, by self-assembly, nanodomains in the shape of cylinders, spheres or lamellae the spatial scale of which varies from a few nanometers to a few tens of nanometers. Among these various structures, cylindrical domains turn out to be particularly suitable for producing interconnect holes in integrated circuits. In an approach known as graphoepitaxy, the self-assembly of a BCP occurs inside a guiding outline or template produced beforehand on a surface. The high lateral confinement induced by the walls of this guiding outline predictably modifies the “natural” free-surface arrangement of the nanodomains (a hexagonal pattern in the case of cylindrical domains perpendicular to the substrate). Thus, it has been proved that the use of a suitable guiding outline allows an arbitrary arrangement of nano-cylinders to be formed, which may correspond to a pattern of interconnect holes in an integrated circuit.
The guiding outlines for graphoepitaxy are typically produced by lithography, and have a shape that inevitably differs from that desired and defined by the lithography mask. It is therefore necessary to check whether the directed self-assembly pattern that will be obtained from a “real” guiding outline—viewed for example by scanning electron microscope—will be sufficiently close to the expected pattern, depending on the targeted application. To do this, it is possible to use numerical simulations based on physical models of the self-assembly process. These physical models may be separated into two broad families: particle-based models and those based on energy fields. By way of nonlimiting example, the following publications may be cited: As regards particle-based models:                “Dissipative particle dynamics study on directed self-assembly in holes” T. Nakano; M. Matsukuma; K. Matsuzaki; M. Muramatsu; T. Tomita; T. Kitano Proc. SPIE 8680, Alternative Lithographic Technologies V, 86801J (Mar. 26, 2013)        “Molecular Dynamics Study of the Role of the Free Surface on Block Copolymer Thin Film Morphology and Alignment Christopher Forrey”, Kevin G. Yager, and Samuel P. Broadaway ACS Nano, 2011, 5 (4), pp 2895-2907        As regards models based on energy fields:        “Computational simulation of block copolymer directed self-assembly in small topographical guiding templates” He Yi; Azat Latypov; H.-S. Philip Wong Proc. SPIE 8680, Alternative Lithographic Technologies V, 86801 L (Mar. 26, 2013)        “Large-scale dynamics of directed self-assembly defects on chemically pre-patterned surface” Kenji Yoshimoto; Takashi Taniguchi Proc. SPIE 8680, Alternative Lithographic Technologies V, 86801I (Mar. 26, 2013);        
All these methods implement iterative algorithms; they are therefore much too slow to be used in the production phase.